1. Field of the Invention
This invention relates to a beam rotation angle detecting apparatus used in a rotary encoder, a linear encoder or the like to optically effect position detection, and a rotation detecting apparatus and a beam rotation angle detecting method.
2. Related Background Art
Heretofore, to obtain the rotation angle of a beam rotating while forming a track as a circle, as disclosed in Japanese Patent Application Laid-Open No. 6-235622 and Japanese Patent Application Laid-Open No. 6-347289, the light receiving position thereof has been detected by a circular ring-shaped or circular light receiving sensor for receiving a beam.
Also, U.S. Pat. No. 4,760,436, discloses that two beams are received by independent arcuate light receiving sensors, and these sensors are used properly in conformity with the rotation angle to thereby detect a round of continuous angle.
In the above-described beam rotation angle detecting apparatus, however, there has been the problem that the rotation angle of a beam cannot be accurately detected under the influence of the deviation between the center of rotation of the beam and the center of the light receiving sensor.